Embedded thermocouple in denervation flex circuit

ABSTRACT

A medical device for sympathetic nerve ablation may include a catheter shaft, an expandable member disposed on or coupled to the catheter shaft, and a plurality of elongate electrode assemblies each constructed as a flexible circuit having a plurality of layers. The expandable member may be configured to shift between an unexpanded configuration and an expanded configuration. The plurality of electrode assemblies may be disposed on an outer surface of the expandable member. Each of the plurality of electrode assemblies may include a temperature sensor within the plurality of layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 61/895,788, filed Oct. 25, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to medical devices for sympathetic nerve ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

A medical device for sympathetic nerve ablation may include a cathetershaft, an expandable balloon disposed on the catheter shaft, the balloonbeing capable of shifting between an unexpanded configuration and anexpanded configuration, and a plurality of elongate electrode assemblieseach constructed as a flexible circuit having a plurality of layers. Theplurality of electrode assemblies may be disposed on an outer surface ofthe balloon. Each of the plurality of electrode assemblies may include atemperature sensor embedded within the plurality of layers.

A medical device for sympathetic nerve ablation may include a cathetershaft, an expandable member coupled to the catheter shaft, theexpandable member being capable of shifting between an unexpandedconfiguration and an expanded configuration, and a plurality of elongateelectrode assemblies each constructed as a flexible circuit having aplurality of layers and a length. The plurality of electrode assembliesmay be disposed on an outer surface of the expandable member. Each ofthe plurality of electrode assemblies may include a sputteredthermocouple positioned between at least one active electrode and atleast one ground electrode.

A medical device for sympathetic nerve ablation within a body passagewaymay include a catheter shaft, an elongate balloon coupled to thecatheter shaft, the balloon being capable of shifting between anunexpanded configuration and an expanded configuration, and a pluralityof elongate electrode assemblies each constructed as a flexible circuithaving a plurality of layers. The plurality of electrode assemblies maybe bonded to an outer surface of the balloon. Each of the plurality ofelectrode assemblies may include a temperature sensor comprising lessthan five percent of a maximum thickness of each of the plurality ofelectrode assemblies.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of an example sympathetic nerve ablationdevice;

FIG. 2 is a perspective view of an example expandable member of asympathetic nerve ablation device;

FIG. 3 is a partial top view of the expandable member of FIG. 2 in anunrolled or flat configuration;

FIG. 4 is a bottom view of a portion of an example electrode assembly;

FIG. 5 is a bottom view of a portion of an example electrode assembly;

FIG. 6 is a partial cross-sectional view of FIG. 4; and

FIG. 7 is a partial cross-sectional view of FIG. 5.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,which are not necessarily to scale, wherein like reference numeralsindicate like elements throughout the several views. The detaileddescription and drawings are intended to illustrate but not limit theclaimed invention. Those skilled in the art will recognize that thevarious elements described and/or shown may be arranged in variouscombinations and configurations without departing from the scope of thedisclosure. The detailed description and drawings illustrate exampleembodiments of the claimed invention.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about”, in thecontext of numeric values, generally refers to a range of numbers thatone of skill in the art would consider equivalent to the recited value(i.e., having the same function or result). In many instances, the term“about” may include numbers that are rounded to the nearest significantfigure. Other uses of the term “about” (i.e., in a context other thannumeric values) may be assumed to have their ordinary and customarydefinition(s), as understood from and consistent with the context of thespecification, unless otherwise specified.

The recitation of numerical ranges by endpoints includes all numberswithin that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5,2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment(s) described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments, whether or not explicitlydescribed, unless clearly stated to the contrary. That is, the variousindividual elements described below, even if not explicitly shown in aparticular combination, are nevertheless contemplated as beingcombinable or arrangable with each other to form other additionalembodiments or to complement and/or enrich the described embodiment(s),as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruptionor modification of select nerve function. In some embodiments, thenerves may be sympathetic nerves. One example treatment is renal nerveablation, which is sometimes used to treat conditions such as or relatedto hypertension, congestive heart failure, diabetes, or other conditionsimpacted by high blood pressure or salt retention. The kidneys produce asympathetic response, which may increase the undesired retention ofwater and/or sodium. The result of the sympathetic response, forexample, may be an increase in blood pressure. Ablating some of thenerves running to the kidneys (e.g., disposed adjacent to or otherwisealong the renal arteries) may reduce or eliminate this sympatheticresponse, which may provide a corresponding reduction in the associatedundesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generatingand control apparatus, often for the treatment of targeted tissue inorder to achieve a therapeutic effect. In some embodiments, the targettissue is tissue containing or proximate to nerves. In otherembodiments, the target tissue is sympathetic nerves, including, forexample, sympathetic nerves disposed adjacent to blood vessels. In stillother embodiments the target tissue is luminal tissue, which may furthercomprise diseased tissue such as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliverenergy in a targeted dosage may be used for nerve tissue in order toachieve beneficial biologic responses. For example, chronic pain,urologic dysfunction, hypertension, and a wide variety of otherpersistent conditions are known to be affected through the operation ofnervous tissue. For example, it is known that chronic hypertension thatmay not be responsive to medication may be improved or eliminated bydisabling excessive nerve activity proximate to the renal arteries. Itis also known that nervous tissue does not naturally possessregenerative characteristics. Therefore it may be possible tobeneficially affect excessive nerve activity by disrupting theconductive pathway of the nervous tissue. When disrupting nerveconductive pathways, it is particularly advantageous to avoid damage toneighboring nerves or organ tissue. The ability to direct and controlenergy dosage is well-suited to the treatment of nerve tissue. Whetherin a heating or ablating energy dosage, the precise control of energydelivery as described and disclosed herein may be directed to the nervetissue. Moreover, directed application of energy may suffice to target anerve without the need to be in exact contact, as would be required whenusing a typical ablation probe. For example, eccentric heating may beapplied at a temperature high enough to denature nerve tissue withoutcausing ablation and without requiring the piercing of luminal tissue.However, it may also be desirable to configure the energy deliverysurface of the present disclosure to pierce tissue and deliver ablatingenergy similar to an ablation probe with the exact energy dosage beingcontrolled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can beassessed by measurement before, during, and/or after the treatment totailor one or more parameters of the treatment to the particular patientor to identify the need for additional treatments. For instance, adenervation system may include functionality for assessing whether atreatment has caused or is causing a reduction in neural activity in atarget or proximate tissue, which may provide feedback for adjustingparameters of the treatment or indicate the necessity for additionaltreatments.

Many of the devices and methods described herein are discussed relativeto renal nerve ablation and/or modulation. However, it is contemplatedthat the devices and methods may be used in other treatment locationsand/or applications where sympathetic nerve modulation and/or othertissue modulation including heating, activation, blocking, disrupting,or ablation are desired, such as, but not limited to: blood vessels,urinary vessels, or in other tissues via trocar and cannula access. Forexample, the devices and methods described herein can be applied tohyperplastic tissue ablation, cardiac ablation, pain management,pulmonary vein isolation, pulmonary vein ablation, tumor ablation,benign prostatic hyperplasia therapy, nerve excitation or blocking orablation, modulation of muscle activity, hyperthermia or other warmingof tissues, etc. The disclosed methods and apparatus can be applied toany relevant medical procedure, involving both human and non-humansubjects. The term modulation refers to ablation and other techniquesthat may alter the function of affected nerves and other tissue.

FIG. 1 is a schematic view of an example sympathetic nerve ablationsystem 100. System 100 may include a sympathetic nerve ablation device120. Sympathetic nerve ablation device 120 may be used to ablate nerves(e.g., renal nerves) disposed adjacent to the kidney K (e.g., renalnerves disposed about a renal artery RA). In use, sympathetic nerveablation device 120 may be advanced through a blood vessel such as theaorta A to a position within the renal artery RA. This may includeadvancing sympathetic nerve ablation device 120 through a guide sheathor catheter 14. When positioned as desired, sympathetic nerve ablationdevice 120 may be activated to activate one or more electrodes (notshown). This may include operatively coupling sympathetic nerve ablationdevice 120 to a control unit 110, which may include an RF generator, soas to supply the desired activation energy to the electrodes. Forexample, sympathetic nerve ablation device 120 may include a wire orconductive member 18 with a first connector 20 that can be connected toa second connector 22 on the control unit 110 and/or a wire 24 coupledto the control unit 110. In at least some embodiments, the control unit110 may also be utilized to supply/receive the appropriate electricalenergy and/or signal to activate one or more sensors disposed at or neara distal end of sympathetic nerve ablation device 120. When suitablyactivated, the one or more electrodes may be capable of ablating tissue(e.g., sympathetic nerves) as described below and the one or moresensors may be used to detect desired physical and/or biologicalparameters.

In some embodiments, the sympathetic nerve ablation device 120 mayinclude an elongate tubular member or catheter shaft 122, as shown inFIG. 2. In some embodiments, the elongate tubular member or cathetershaft 122 may be configured to be slidingly advanced over a guidewire orother elongate medical device to a target site. In some embodiments, theelongate tubular member or catheter shaft 122 may be configured to beslidingly advanced within a guide sheath or catheter 14 to a targetsite. In some embodiments, the elongate tubular member or catheter shaft122 may be configured to be advanced to a target site over a guidewire,within a guide sheath or catheter 14, or a combination thereof. Anexpandable member 130 may be disposed at, on, about, or near a distalregion of the elongate tubular member or catheter shaft 122. In someembodiments, the expandable member 130 may be a compliant or anon-compliant balloon. In some embodiments, the expandable member 130may be capable of shifting between an unexpanded configuration and anexpanded configuration.

For example, as shown in FIG. 2, in some embodiments, one or moreelectrode assemblies may be arranged on the expandable member 130, shownin an expanded state, according to a plurality of generally cylindricaltreatment zones A-D. In other embodiments, the expandable member 130 orother components of the treatment system may include additionalelectrode assemblies that are not in a treatment zone or are otherwisenot used or configured to deliver a treatment energy.

The treatment zones A-D and associated electrode assemblies 140 a-d arefurther illustrated in FIG. 3, which is an “unrolled” depiction of aportion of the expandable member 130 of FIG. 2. The treatment zones A-Dmay be longitudinally adjacent to one another along longitudinal axisL-L, and may be configured such that energy applied by the electrodeassemblies create treatments that may or may not overlap. Treatmentsapplied by the longitudinally adjacent bipolar electrode assemblies 140a-d may be circumferentially non-continuous along longitudinal axis L-L.For example, with reference to FIG. 3, lesions created in treatment zoneA may in some embodiments minimize overlap about a circumference(laterally with respect to L-L in this view) with lesions created intreatment zone B. In other embodiments, however, the energy applied bythe electrode assemblies, such as the electrode assemblies shown in FIG.3, may overlap, longitudinally, circumferentially, and/or in other ways,to at least some extent. Each electrode pad assembly may include fourelements, which are a distal electrode pad 150 a-d, intermediate tail160 a-d, proximal electrode pad 170 a-d, and proximal tail 180 b,d (notshown for electrode pad assemblies 140 a and 140 c).

FIG. 4 shows a bottom view of an example electrode assembly 200, or aview of a bottom side of the electrode assembly 200 that may face, maybe in contact with, and/or may be attached and/or bonded directly to anouter surface of the expandable member 130. The electrode assembly 200may be constructed as a flexible circuit having a plurality of layers.Such layers may be continuous or non-contiguous (i.e., made up ofdiscrete portions). As shown in cross-section in FIG. 6, a base layer202 of insulation may provide a foundation for the electrode assembly200. The base layer 202 may be constructed from a polymer such aspolyimide, although other materials are contemplated. In someembodiments, the base layer 202 may be about 0.010 mm to about 0.020 mmthick. In some embodiments, the base layer 202 may be about 0.015 mmthick. Other suitable thicknesses are also contemplated. For reference,the base layer 202 may form the bottom side of the electrode assembly200 that may face, may be in contact with, and/or may be attached and/orbonded directly to the outer surface of the expandable member 130. FIG.6 illustrates an end view of the bottom view shown in FIG. 4, and thusmay appear to be inverted with respect to certain relative terms usedherein.

A conductive layer 204 may include a plurality of discrete conductivetraces layered on top of the base layer 202. In some embodiments, theplurality of discrete conductive traces may be separated laterally by anon-conductive material. The plurality of discrete conductive traces ofthe conductive layer 204 may include, for example, a layer ofelectrodeposited copper or rolled-annealed copper. Other suitableconductive materials are also contemplated. In some embodiments, theconductive layer 204 and/or the plurality of discrete conductive tracesmay be about 0.010 mm to about 0.030 mm thick. In some embodiments, theconductive layer 204 and/or the plurality of discrete conductive tracesmay be about 0.018 mm thick. Other suitable thicknesses are alsocontemplated.

An insulating layer 206 may be discretely or continuously layered on topof the conductive layer 204, such that the conductive layer 204 may befluidly sealed between the base layer 202 and the insulating layer 206.In other words, the insulating layer 206 may form a top side or surfaceof the electrode assembly 200 that may face away from the outer surfaceof the expandable member 130. The relationship between the base layer202, the conductive layer 204, and the insulating layer 206 isillustrative, and other constructions are contemplated. Like the baselayer 202, the insulating layer 206 may be constructed from a polymersuch as polyimide, although other materials are contemplated. In someembodiments, the insulating layer 206 may be from about 0.010 mm thickto about 0.020 mm thick. In some embodiments, the insulating layer 206may be about 0.013 mm thick. Other suitable thicknesses are alsocontemplated. In some embodiments, the insulating layer 206 may be acomplete or partial polymer coating, such as PTFE or silicone. Othermaterials are also contemplated.

In some embodiments, the plurality of layers (i.e., the base layer 202,the conductive layer 204, and the insulating layer 206) may combine todefine a thickness of the flexible circuit. In some embodiments, thethickness of the flexible circuit may be substantially constant over thelength of the flexible circuit and/or the electrode assembly 200. Insome embodiments, the thickness of the flexible circuit may be about0.046 mm.

The electrode assembly 200 shown in FIG. 4 may include a distalelectrode pad 208. In this region, the base layer 202 may form arectangular shape. This is not intended to be limiting. Other shapes arecontemplated. As shown, the electrode assembly 200 may include aplurality of openings extending therethrough to provide for addedflexibility, and the pads and other portions of the assemblies mayinclude rounded or curved corners, transitions and other portions. Insome instances, the openings and rounded/curved features may enhance theassembly's resistance to delamination from the expandable member 130, asmay occur, in some instances, when the expandable member 130 isrepeatedly expanded and collapsed (which may also entail deployment fromand withdrawal into a protective sheath), such as may be needed whenmultiple sites are treated during a procedure.

As discussed above, the distal electrode pad 208 may include a pluralityof discrete conductive traces layered on top of the base layer 202. Theplurality of discrete conductive traces may include a ground electrodetrace 210, an active electrode trace 212, and a sensor trace 214. Theground electrode trace 210 may include an elongated ground electrodesupport 216 laterally offset from a sensor ground pad 218. The sensorground pad 218 may be electrically coupled to the elongated groundelectrode support 216 of the ground electrode trace 210 and may becentrally located on the distal electrode pad 208. A bridge 220 mayconnect a distalmost portion of the sensor ground pad 218 to a distalportion of the elongated ground electrode support 216 of the groundelectrode trace 210. The bridge 220 may taper down in width as ittravels to the sensor ground pad 218. In some embodiments, the bridge220 may have a relatively uniform and thin width to enable a desiredamount of flexibility. The elongated ground electrode support 216 maytaper down in width at its proximal end, however, this is not required.In some embodiments, the elongated ground electrode support 216 mayabruptly transition to a much thinner trace at its proximal portion, toenable a desired amount of flexibility. The active electrode trace 212may include an elongated active electrode support 217 laterally offsetfrom the elongated ground electrode support 216, the sensor ground pad218, and/or a sensor power pad 224. The sensor power pad 224 may beelectrically coupled to the sensor trace 214 and may be centrallylocated on the distal electrode pad 208. The elongated active electrodesupport 217 may taper down in width at its proximal end, however, thisis not required. In some embodiments, the elongated active electrodesupport 217 may abruptly transition to a much thinner trace at itsproximal portion, to enable a desired amount of flexibility. Generally,the curvature of the traces where necking is shown may be optimized toreduce balloon recapture forces and to reduce the potential for anysnagging that sharper contours may present. The shape and position ofthe traces may also be optimized to provide dimensional stability to theelectrode assembly 200 as a whole, so as to prevent distortion duringdeployment and use.

As shown in FIG. 4, the ground electrode trace 210 and active electrodetrace 212 may each include a plurality of electrodes 222. In someembodiments, at least one electrode may be provided for each electrodetrace, however, more or less may be used.

For example, in some embodiments, three electrodes may be provided foreach electrode trace. The plurality of electrodes 222 may protrude aboveand/or extend through the insulating layer 206. In some embodiments, theplurality of electrodes 222 may include at least one active electrodeand at least one ground electrode attached and/or electrically connectedto the elongated active electrode support 217 and the elongated groundelectrode support 216, respectively. In some embodiments, a plurality ofelectrodes 222 may be attached and/or electrically connected to theelongated ground electrode support 216, thereby defining a plurality ofground electrodes, and/or the elongated active electrode support 217,thereby defining a plurality of active electrodes. In some embodiments,the plurality of electrodes 222 may be from about 0.030 mm thick toabout 0.070 mm thick. In some embodiments, the plurality of electrodes222 may be about 0.051 mm thick. In some embodiments, the plurality ofelectrodes 222 may extend about 0.020 mm to about 0.050 mm above theinsulating layer 206. In some embodiments, the plurality of electrodes222 may extend about 0.038 mm above the insulating layer 206.Additionally, each electrode may have radiused corners to reducetendency to snag on other devices and/or tissue. Although the abovedescription of the plurality of electrodes and the traces associatedwith them has been described in the context of a bi-polar electrodeassembly, those of skill in the art will recognize that the sameelectrode assembly may function in a monopolar mode as well. Forinstance, as one non-limiting example, the plurality of electrodesassociated with active electrode traces 212 and 242 may be used asmonopolar electrodes, with ground electrode trace 210 disconnectedduring energization of those electrodes.

The sensor trace 214 may be centrally located on the distal electrodepad 208 and may include a sensor power pad 224 facing and/or adjacentthe sensor ground pad 218. These pads may connect to power and groundpoles of a temperature sensor 226, such as a thermistor. In someembodiments, the temperature sensor 226 may be proximally connected tothe sensor power pad 224 and may be distally connected to the sensorground pad 218. In some embodiments, the temperature sensor 226 may bein direct contact with the sensor power pad 224 and/or the sensor groundpad 218. In some embodiments, the temperature sensor 226 may be attachedand/or electrically connected to the sensor power pad 224 and/or thesensor ground pad 218 by soldering, welding, and the like, or othersuitable means. In some embodiments, the temperature sensor 226 may bedisposed or positioned between at least one active electrode and atleast one ground electrode. In some embodiments, the temperature sensor226 may be disposed or positioned between the plurality of activeelectrodes and the plurality of ground electrodes.

In some embodiments, the temperature sensor 226 may have a length ofabout 0.500 mm to about 2.000 mm, and a width of about 0.200 mm to about0.800 mm. In some embodiments, the temperature sensor 226 may have alength of about 1.000 mm and a width of about 0.500 mm. To help reduceoverall thickness, the temperature sensor 226 may be positioned withinan opening in the base layer 202. In some embodiments, the temperaturesensor 226 may protrude outwardly from the base layer 202 by about 0.050mm to about 0.200 mm. In some embodiments, the temperature sensor 226may have a thickness of about 0.115 mm and may protrude outwardly fromthe base layer 202 by about 0.100 mm. In some embodiments, an overallthickness of the electrode assembly 200 at the temperature sensor 226(i.e., including the plurality of layers and the temperature sensor 226)may be about 0.146 mm. In some embodiments, the temperature sensor 226may comprise more than 65% of the overall thickness of the electrodeassembly 200 at the temperature sensor 226.

In some embodiments, a maximum thickness of the electrode assembly 200(including the plurality of layers, the temperature sensor 226, and theplurality of electrodes 222) may be from about 0.150 mm to about 0.200mm. In some embodiments, the maximum thickness of the electrode assembly200 may be about 0.184 mm. In some embodiments, the temperature sensor226 may comprise more than 50% of the maximum thickness of the electrodeassembly 200.

In some embodiments, the temperature sensor 226 may be a thermistor. Asshown, the temperature sensor 226 may be disposed on a non-tissuecontacting side (i.e., bottom side) of the distal electrode pad 208and/or the electrode assembly 200. Accordingly, the temperature sensor226 may be captured between the electrode assembly 200 and theexpandable member 130 when incorporated into an ablation device 120.This may be advantageous since surface-mounted electrical components,like thermistors, may typically have sharp edges and corners, which mayget caught on tissue and possibly cause problems in balloon deploymentand/or retraction. This arrangement may also keep soldered connectionsfrom making contact with blood, since solder is typicallynon-biocompatible. Further, due to the placement of the temperaturesensor 226 between the plurality of active electrodes contacting theelongated active electrode support 217 and the plurality of groundelectrodes contacting the elongated ground electrode support 216, thetemperature sensor 226 may measure temperature representative of theplurality of electrodes 222 and/or tissue adjacent to and/or in contactwith the plurality of electrodes 222.

The size and/or thickness of the electrode assembly 200 at thetemperature sensor 226 may create a protrusion extending outward fromthe outer surface of the expandable member 130. Following a treatmentprocedure, the expandable member 130 may be collapsed to a collapseddelivery configuration, as discussed further herein, and the ablationdevice 120 may be retracted within the guide sheath or catheter 14.Significant protrusion(s) may make refraction into the guide sheath orcatheter 14 more difficult and/or require a larger diameter guide sheathor catheter 14 than would otherwise be desired. Additionally, theprotrusion(s) may negatively impact the foldability characteristics ofthe expandable member 130, both for delivery and for withdrawal.

Moving proximally from the distal electrode pad 208, the combined baselayer 202, conductive layer 204, and insulating layer 206 may reduce inlateral width to an intermediate tail 228. Here, as shown in FIG. 4, theconductive layer 204 may be formed to include an intermediate groundline 230, intermediate active electrode line 232, and intermediatesensor line 234, which may be respectively coextensive traces of theground electrode trace 210, active electrode trace 212, and sensor trace214 of the distal electrode pad 208.

Continuing to move proximally from the intermediate tail 228, thecombined base layer 202, conductive layer 204, and insulating layer 206may increase in lateral width to form a proximal electrode pad 236. Theproximal electrode pad 236 may be constructed similarly to the distalelectrode pad 208, with the electrode geometry and temperature sensorarrangement being essentially identical, although various differencesmay be present. However, as shown, the proximal electrode pad 236 may belaterally offset from the distal electrode pad 208 with respect to acentral longitudinal axis G-G extending along the intermediate groundline 230. The intermediate active electrode line 232 and intermediatesensor line 234 may be laterally coextensive with the proximal electrodepad 236 on parallel respective axes with respect to central axis G-G.

From the proximal electrode pad 236, the combined base layer 202,conductive layer 204, and insulating layer 206 may reduce in lateralwidth to form a proximal tail 238. The proximal tail 238 may include aproximal ground line 240, proximal active electrode line 242, andproximal sensor line 244, as well as the intermediate active electrodeline 232 and intermediate sensor line 234. The proximal tail 238 mayinclude connectors (not shown) to enable coupling to one or moresub-wiring harnesses and/or connectors and ultimately to control unit110. Each of these lines may be extended along parallel respective axeswith respect to central axis G-G.

As shown, the electrode assembly 200 may have an asymmetric arrangementof the distal electrode pad 208 and proximal electrode pad 236, aboutcentral axis G-G. Further, the ground electrodes of both electrode padsmay be substantially aligned along central axis G-G, along with theintermediate and proximal ground lines 230/240. It has been found thatthis arrangement may present certain advantages. For example, byessentially sharing the same ground trace, the width of the proximaltail may be only about one and a half times that of the intermediatetail 228, rather than being approximately twice as wide if eachelectrode pad had independent ground lines. Thus, the proximal tail 238may be narrower than two intermediate tails 228 positioned side-by-side.

The use of medical devices that include a balloon with one or moreelectrode assemblies coupled thereto, for example as described herein,may be desirable. In some instances, however, the electrode assembliesmay include relatively stiff and/or bulky materials or elements.Accordingly, when the balloon is deflated following a treatmentprocedure, the electrode assembly may tend to flatten and/or widen out.When so configured, the one or more electrode assemblies, and/orcomponents or edges thereof, might catch on the edge of a guide catheterwhen proximally retracting the medical device (e.g., including theaffixed electrode assemblies) into the guide catheter. Disclosed hereinare medical devices that include structural features that may reduce thesize of an electrode assembly and the likelihood of an electrodeassembly or other structures of the medical device “catching” on the endof a guide catheter (or other device) when being retracted, for example,into the guide catheter, thus resulting in reduced withdrawal forces.

FIG. 5 shows a bottom view of an example electrode assembly 300, or aview of a bottom side of the electrode assembly 300 that may face, maybe in contact with, and/or may be attached and/or bonded directly to anouter surface of the expandable member 130. The electrode assembly 300may be constructed as a flexible circuit having a plurality of layers.Such layers may be continuous or non-contiguous (i.e., made up ofdiscrete portions). As shown in cross-section in FIG. 7, a base layer302 of insulation may provide a foundation for the electrode assembly300. The base layer 302 may be constructed from a polymer such aspolyimide, although other materials are contemplated. In someembodiments, the base layer 302 may be about 0.010 mm to about 0.020 mmthick. In some embodiments, the base layer 302 may be about 0.015 mmthick. Other suitable thicknesses are also contemplated. For reference,the base layer 302 may form the bottom side of the electrode assembly300 that may face, may be in contact with, and/or may be attached and/orbonded directly to the outer surface of the expandable member 130. FIG.7 illustrates an end view of the bottom view shown in FIG. 5, and thusmay appear to be inverted with respect to certain relative terms usedherein.

A conductive layer 304 may include a plurality of discrete conductivetraces layered on top of the base layer 302. In some embodiments, theplurality of discrete conductive traces may be separated laterally by anon-conductive material. The plurality of discrete conductive traces ofthe conductive layer 304 may include, for example, a layer ofelectrodeposited copper or rolled-annealed copper. Other suitableconductive materials are also contemplated. In some embodiments, theconductive layer 304 and/or the plurality of discrete conductive tracesmay be about 0.010 mm to about 0.030 mm thick. In some embodiments, theconductive layer 304 and/or the plurality of discrete conductive tracesmay be about 0.018 mm thick. Other suitable thicknesses are alsocontemplated.

An insulating layer 306 may be discretely or continuously layered on topof the conductive layer 304, such that the conductive layer 304 may befluidly sealed between the base layer 302 and the insulating layer 306.In other words, the insulating layer 306 may form a top side or surfaceof the electrode assembly 300 that may face away from the outer surfaceof the expandable member 130. Like the base layer 302, the insulatinglayer 306 may be constructed from a polymer such as polyimide, althoughother materials are contemplated. In some embodiments, the insulatinglayer 306 may be from about 0.010 mm thick to about 0.020 mm thick. Insome embodiments, the insulating layer 306 may be about 0.013 mm thick.Other suitable thicknesses are also contemplated. In some embodiments,the insulating layer 306 may be a complete or partial polymer coating,such as PTFE or silicone. Other materials are also contemplated.

In some embodiments, the plurality of layers (i.e., the base layer 302,the conductive layer 304, and the insulating layer 306) may combine todefine a thickness of the flexible circuit. In some embodiments, thethickness of the flexible circuit may vary over the length of theflexible circuit and/or the electrode assembly 300. In some embodiments,the thickness of the flexible circuit may be substantially constant overthe length of the flexible circuit and/or the electrode assembly 300. Insome embodiments, the thickness of the flexible circuit may be about0.046 mm.

The electrode assembly 300 shown in FIG. 5 may include a distalelectrode pad 308. In this region, the base layer 302 may form arectangular shape. This is not intended to be limiting. Other shapes arecontemplated. As shown, the electrode assembly 300 may include aplurality of openings extending therethrough to provide for addedflexibility, and the pads and other portions of the assemblies mayinclude rounded or curved corners, transitions and other portions. Insome instances, the openings and rounded/curved features may enhance theassembly's resistance to delamination from the expandable member 130, asmay occur, in some instances, when the expandable member 130 isrepeatedly expanded and collapsed (which may also entail deployment fromand withdrawal into a protective sheath), such as may be needed whenmultiple sites are treated during a procedure.

As discussed above, the distal electrode pad 308 may include a pluralityof discrete conductive traces layered on top of the base layer 302. Theplurality of discrete conductive traces may include a ground electrodetrace 310, an active electrode trace 312, and a sensor trace 314. Theground electrode trace 310 may include an elongated ground electrodesupport 316 laterally offset from a sensor ground pad 318. The sensorground pad 318 may be electrically coupled to the elongated groundelectrode support 316 of the ground electrode trace 310 and may becentrally located on the distal electrode pad 308. A bridge 320 mayconnect a distalmost portion of the sensor ground pad 318 to a distalportion of the elongated ground electrode support 316 of the groundelectrode trace 310. The bridge 320 may taper down in width as ittravels to the sensor ground pad 318. In some embodiments, the bridge320 may have a relatively uniform and thin width to enable a desiredamount of flexibility. The elongated ground electrode support 316 maytaper down in width at its proximal end, however, this is not required.In some embodiments, the elongated ground electrode support 316 mayabruptly transition to a much thinner trace at its proximal portion, toenable a desired amount of flexibility. The active electrode trace 312may include an elongated active electrode support 317 laterally offsetfrom the elongated ground electrode support 316 and the sensor groundpad 318. The sensor trace 314 may be centrally located on the distalelectrode pad 308 and/or aligned with the sensor ground pad 318. Theelongated active electrode support 317 may taper down in width at itsproximal end, however, this is not required. In some embodiments, theelongated active electrode support 317 may abruptly transition to a muchthinner trace at its proximal portion, to enable a desired amount offlexibility. Generally, the curvature of the traces where necking isshown may be optimized to reduce balloon recapture forces and to reducethe potential for any snagging that sharper contours may present. Theshape and position of the traces may also be optimized to providedimensional stability to the electrode assembly 300 as a whole, so as toprevent distortion during deployment and use.

As shown in FIG. 5, the ground electrode trace 310 and active electrodetrace 312 may each include a plurality of electrodes 322. In someembodiments, at least one electrode may be provided for each electrodetrace, however, more or less may be used. For example, in someembodiments, three electrodes may be provided for each electrode trace.The plurality of electrodes 322 may protrude above and/or extend throughthe insulating layer 306. In some embodiments, the plurality ofelectrodes 322 may include at least one active electrode and at leastone ground electrode attached and/or electrically connected to theelongated active electrode support 317 and the elongated groundelectrode support 316, respectively. A plurality of electrodes 322 maybe attached and/or electrically connected to the elongated groundelectrode support 316, thereby defining a plurality of groundelectrodes, and/or the elongated active electrode support 317, therebydefining a plurality of active electrodes. In some embodiments, theplurality of electrodes 322 may be from about 0.030 mm thick to about0.070 mm thick. In some embodiments, the plurality of electrodes 322 maybe about 0.051 mm thick. In some embodiments, the plurality ofelectrodes 322 may extend about 0.020 mm to about 0.050 mm above theinsulating layer 306. In some embodiments, the plurality of electrodes322 may extend about 0.038 mm above the insulating layer 306.Additionally, each electrode may have radiused corners to reducetendency to snag on other devices and/or tissue. Although the abovedescription of the plurality of electrodes and the traces associatedwith them has been described in the context of a bi-polar electrodeassembly, those of skill in the art will recognize that the sameelectrode assembly may function in a monopolar mode as well. Forinstance, as one non-limiting example, the plurality of activeelectrodes associated with active electrode traces 312 and 342 may beused as monopolar electrodes, with ground electrode trace 310disconnected during energization of those electrodes.

The sensor trace 314 may be centrally located on the distal electrodepad 308 and may be electrically-connected to the sensor ground pad 318to form a temperature sensor 326, such as a thermocouple (for example,Type T configuration: Copper/Constantan). In some embodiments, thetemperature sensor 326 may be disposed or positioned between at leastone active electrode and at least one ground electrode. In someembodiments, the temperature sensor 326 may be disposed or positionedbetween the plurality of active electrodes and the plurality of groundelectrodes. A thermocouple may generate a voltage differential at thejunction of two dissimilar metals based upon the temperature at thejunction, as is known in the art. In some embodiments, an isothermaljunction may be formed at a proximal end of the electrode assembly 300,spaced apart from and thermally isolated from the electrode pad(s)and/or the plurality of electrodes. In some embodiments, the sensorground pad 318 may be formed as a discrete trace of electrodepositedcopper within the conductive layer 304, as discussed above. In someembodiments, the distal end portion of the sensor trace 314, and in somecases the entire sensor trace 314 may be formed from, for example,constantan (i.e., copper-nickel alloy), nickel-chromium, or othersuitable conductive material. In some embodiments, the temperaturesensor 326 may be formed by a distal end portion of the sensor trace 314overlapping the sensor ground pad 318, such that the sensor trace 314and the sensor ground pad 318 are in direct contact. In someembodiments, the temperature sensor 326 may be formed by sputtering thedistal end portion of the sensor trace 314 over the sensor ground pad318, thereby forming a sputtered thermocouple, or other suitable means.

In some embodiments, the temperature sensor 326 may have a length ofabout 0.100 mm to about 2.000 mm, and a width of about 0.100 mm to about0.800 mm. In some embodiments, the temperature sensor 326 may have alength of about 1.000 mm and a width of about 0.500 mm. In anotherembodiment, the temperature sensor may have a length of about 0.2 mm anda width of 0.01 mm. Other sizes and/or dimensions are contemplated. Anadvantage of utilizing a sputtering process to form the temperaturesensor 326 is that sputtering reduces the overall or maximum thicknessof the electrode assembly 300. In some embodiments, the distal endportion of the sensor trace 314 overlapping the sensor ground pad 318(i.e., forming the temperature sensor 326) may have a thickness of about0.0002 mm. In other words, the thickness of a sputtered thermocouple maybe negligible compared to a thermistor. In some embodiments, an overallthickness of the electrode assembly 300 at the temperature sensor 326(i.e., including the plurality of layers and the temperature sensor 326)may be about 0.046 mm. In some embodiments, the temperature sensor 326may comprise less than 5% of the overall thickness of the electrodeassembly 300 at the temperature sensor 326. In some embodiments, thetemperature sensor 326 may comprise less than 1% of the overallthickness of the electrode assembly 300 at the temperature sensor 326.

In some embodiments, the temperature sensor 326 may be embedded betweenthe base layer 302 and the insulating layer 306, such that thetemperature sensor 326 is fluidly sealed within the flexible circuitand/or the electrode assembly 300. In other words, in some embodiments,the temperature sensor 326 may not be positioned on an outer surface ofthe electrode assembly 300, whereas the temperature sensor 226(thermistor) is positioned on or extending outwardly from the outersurface of the electrode assembly 200. In some embodiments, noprotrusion may be formed on the bottom side of the electrode assembly300 at the temperature sensor 326. For example, in a flattenedconfiguration (e.g., FIG. 3), the bottom side of the electrode assembly300 that faces the outer surface of the expandable member 130 may forman uninterrupted surface. In some embodiments, in a flattenedconfiguration (e.g., FIG. 3), the bottom side of the electrode assemblymay include (and/or the uninterrupted surface may form) an essentiallycontinuously planar surface with the temperature sensor 326 in placeon/in the electrode assembly 300. In other words, the temperature sensor326 does not protrude or extend outwardly through or from the base layer302. A lack of protrusion of the bottom side of the electrode assembly300 may enhance adhesion of the electrode assembly 300 to the expandablemember 130, as well as foldability of the expandable member 130 in thecollapsed delivery configuration. In some embodiments, the plurality oflayers may form a substantially constant thickness over the length ofthe electrode assembly 300. In some embodiments, a maximum thickness ofthe electrode assembly 300 (including the plurality of layers, thetemperature sensor 326, and the plurality of electrodes 322) may be fromabout 0.035 mm to about 0.100 mm. In some embodiments, the maximumthickness of the electrode assembly 300 may be about 0.084 mm. In someembodiments, the temperature sensor 326 may comprise less than 0.5% ofthe maximum thickness of the electrode assembly 300.

Similar to the temperature sensor 226 above, placement of thetemperature sensor 326 between the plurality of active electrodescontacting the elongated active electrode support 317 and the pluralityof ground electrodes contacting the elongated ground electrode support316, the temperature sensor 326 may measure temperature representativeof the plurality of electrodes 322 and/or tissue adjacent to and/or incontact with the plurality of electrodes 322.

The relative size and/or thickness of the electrode assembly 300 at thetemperature sensor 326 (or the lack thereof) may avoid creating aprotrusion extending outward from the outer surface of the expandablemember 130. Following a treatment procedure, the expandable member 130may be collapsed to a collapsed delivery configuration, as discussedfurther herein, and the ablation device 120 may be retracted within theguide sheath or catheter 14. The lack of protrusion(s) may makeretraction into the guide sheath or catheter 14 easier and/or permit theuse of a smaller diameter guide sheath or catheter 14 than wouldotherwise be required. Additionally, the lack of protrusion(s) maypositively affect the foldability characteristics of the expandablemember 130, both for delivery and for withdrawal.

Moving proximally from the distal electrode pad 308, the combined baselayer 302, conductive layer 304, and insulating layer 306 may reduce inlateral width to an intermediate tail 328. Here, as shown in FIG. 5, theconductive layer 304 may be formed to include an intermediate groundline 330, intermediate active electrode line 332, and intermediatesensor line 334, which may be respectively coextensive traces of theground electrode trace 310, active electrode trace 312, and sensor trace314 of the distal electrode pad 308.

Continuing to move proximally from the intermediate tail 328, thecombined base layer 302, conductive layer 304, and insulating layer 306may increase in lateral width to form a proximal electrode pad 336. Theproximal electrode pad 336 may be constructed similarly to the distalelectrode pad 308, with the electrode geometry and temperature sensorarrangement being essentially identical, although various differencesmay be present. However, as shown, the proximal electrode pad 336 may belaterally offset from the distal electrode pad 308 with respect to acentral longitudinal axis G-G extending along the intermediate groundline 330. The intermediate active electrode line 332 and intermediatesensor line 334 may be laterally coextensive with the proximal electrodepad 336 on parallel respective axes with respect to central axis G-G.

From the proximal electrode pad 336, the combined base layer 302,conductive layer 304, and insulating layer 306 may reduce in lateralwidth to form a proximal tail 338. The proximal tail 338 may include aproximal ground line 340, proximal active electrode line 342, andproximal sensor line 344, as well as the intermediate active electrodeline 332 and intermediate sensor line 334. The proximal tail 338 mayinclude connectors (not shown) to enable coupling to one or moresub-wiring harnesses and/or connectors and ultimately to control unit110. Each of these lines may be extended along parallel respective axeswith respect to central axis G-G.

As shown, the electrode assembly 300 may have an asymmetric arrangementof the distal electrode pad 308 and proximal electrode pad 336, aboutcentral axis G-G. Further, the ground electrodes of both electrode padsmay be substantially aligned along central axis G-G, along with theintermediate and proximal ground lines 330/340. It has been found thatthis arrangement may present certain advantages. For example, byessentially sharing the same ground trace, the width of the proximaltail may be only about one and a half times that of the intermediatetail 328, rather than being approximately twice as wide if eachelectrode pad had independent ground lines. Thus, the proximal tail 338may be narrower than two intermediate tails 328 positioned side-by-side.

In some embodiments, the electrode assembly(s) 300 may be disposed alongor otherwise define pre-determined fold lines along which the expandablemember 130 may fold after deflation. In some embodiments, thepre-determined fold lines may aid in re-folding of the expandable member130.

In some embodiments, the electrode assembly(s) 300 may be substantiallylinear, extending along or at an angle to the longitudinal axis L-Lalong the entire length of the expandable member 130. In someembodiments, the electrode assemblies may extend parallel to thelongitudinal axis in a proximal region, and then be bent into an angledorientation in a distal region (not shown). The electrode assembly(s)300 may cause the balloon to fold along the lines of the electrodeassembly(s) 300, reducing the withdrawal force needed to withdraw theablation device 120 into the guide sheath or catheter 14, and allowingthe use of a smaller diameter guide sheath. For example, a 6 Fr or 7 Frguide catheter 14 may be used, providing advantages in certainprocedures, (e.g., renal procedures), where 8 Fr guide catheters havebeen previously used. The electrode assembly(s) 300 may also reduceshear force or improve balloon refold profile efficiency, therebyreducing delamination of the electrode assembly(s) 300 from theexpandable member 130.

In use, the ablation device 120 may be advanced through a blood vesselor body passageway to a position adjacent to a target tissue (e.g.,within a renal artery), in some cases with the aid of a delivery sheathor catheter 14. In some embodiments, the target tissue may be one ormore sympathetic nerves disposed about the blood vessel. In someembodiments, the control unit 110 may be operationally coupled to theablation device 120, which may be inserted into a blood vessel or bodypassageway such that an expandable member 130 (having a plurality ofelectrode assemblies 300) may be placed adjacent to the target tissuewhere therapy is required. Placement of the ablation device 120 adjacentthe target tissue where therapy is required may be performed accordingto conventional methods, (e.g., over a guidewire under fluoroscopicguidance). When suitably positioned, the expandable member 130 may beexpanded from a collapsed delivery configuration to an expandedconfiguration, for example by pressurizing fluid from about 2-10 atm inthe case of a balloon. This may place/urge the plurality of electrodesagainst the wall of the blood vessel. The plurality of active electrodesmay be activated. Ablation energy may be transmitted from the pluralityof active electrodes through the target tissue (where sympathetic nervesmay be ablated, modulated, or otherwise impacted), and back through theplurality of ground electrodes, in a bipolar configuration, or backthrough the common ground electrode, in a monopolar configuration.Following treatment, the expandable member 130 may be collapsed to thecollapsed delivery configuration for retraction into the guide sheath orcatheter 14 and subsequent withdrawal from the blood vessel or bodypassageway.

The materials that can be used for the various components of theablation device 120 (and/or other devices disclosed herein) may includethose commonly associated with medical devices. For simplicity purposes,the following discussion makes reference to the ablation device 120.However, this is not intended to limit the devices and methods describedherein, as the discussion may be applied to other similar tubularmembers and/or expandable members and/or components of tubular membersand/or expandable members disclosed herein.

The ablation device 120 and the various components thereof may be madefrom a metal, metal alloy, polymer (some examples of which are disclosedbelow), a metal-polymer composite, ceramics, combinations thereof, andthe like, or other suitable material. Some examples of suitable polymersmay include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions of the ablation device 120 mayalso be doped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of the ablation device 120 in determining its location. Someexamples of radiopaque materials can include, but are not limited to,gold, platinum, palladium, tantalum, tungsten alloy, polymer materialloaded with a radiopaque filler, and the like. Additionally, otherradiopaque marker bands and/or coils may also be incorporated into thedesign of the ablation device 120 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility may be imparted into the ablation device 120. For example,portions of device, may be made of a material that does notsubstantially distort the image and create substantial artifacts (i.e.,gaps in the image). Certain ferromagnetic materials, for example, maynot be suitable because they may create artifacts in an MRI image. Insome of these and in other embodiments, portions of the ablation device120 may also be made from a material that the MRI machine can image.Some materials that exhibit these characteristics include, for example,tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such asELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenumalloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, andthe like, and others.

U.S. patent application Ser. No. 13/750,879, filed on Jan. 25, 2013,entitled “METHODS AND APPARATUSES FOR REMODELING TISSUE OF OR ADJACENTTO A BODY PASSAGE”, now U.S. Patent Publication US20130165926A1 isherein incorporated by reference.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for sympathetic nerve ablation,comprising: a catheter shaft; an expandable balloon disposed on thecatheter shaft, the balloon being capable of shifting between anunexpanded configuration and an expanded configuration; and a pluralityof elongate electrode assemblies each constructed as a flexible circuithaving a plurality of layers, the plurality of electrode assembliesdisposed on an outer surface of the balloon; wherein each of theplurality of electrode assemblies includes a temperature sensor embeddedwithin the plurality of layers.
 2. The medical device of claim 1,wherein the electrode assemblies each include a plurality of electrodes.3. The medical device of claim 2, wherein the electrode assemblies eachinclude a plurality of active electrodes and a plurality of groundelectrodes.
 4. The medical device of claim 3, wherein the temperaturesensor is positioned between the plurality of active electrodes and theplurality of ground electrodes.
 5. The medical device of claim 1,wherein a bottom side of each of the plurality of electrode assembliesis attached to the outer surface of the balloon.
 6. The medical deviceof claim 1, wherein the balloon is a non-compliant balloon and theplurality of electrode assemblies unfold and fold with the balloon. 7.The medical device of claim 1, wherein the plurality of layers and thetemperature sensor combine to define an overall thickness of eachelectrode assembly at the temperature sensor.
 8. The medical device ofclaim 7, wherein the temperature sensor is a sputtered thermocouple. 9.The medical device of claim 7, wherein the temperature sensor comprisesless than 5 percent of the overall thickness.
 10. The medical device ofclaim 7, wherein the temperature sensor comprises less than 1 percent ofthe overall thickness.
 11. A medical device for sympathetic nerveablation, comprising: a catheter shaft; an expandable member coupled tothe catheter shaft, the expandable member being capable of shiftingbetween an unexpanded configuration and an expanded configuration; and aplurality of elongate electrode assemblies each constructed as aflexible circuit having a plurality of layers and a length, theplurality of electrode assemblies disposed on an outer surface of theexpandable member; wherein each of the plurality of electrode assembliesincludes a sputtered thermocouple positioned between at least one activeelectrode and at least one ground electrode.
 12. The medical device ofclaim 11, wherein the sputtered thermocouple is embedded between two ofthe plurality of layers.
 13. The medical device of claim 11, wherein aside of the plurality of electrode assemblies that faces the expandablemember forms an uninterrupted surface.
 14. The medical device of claim13, when the plurality of electrode assemblies is disposed in aflattened configuration, the uninterrupted surface is substantiallyplanar.
 15. The medical device of claim 11, wherein the plurality oflayers forms a substantially constant thickness over the length of eachelectrode assembly.
 16. The medical device of claim 11, wherein the atleast one active electrode and the at least one ground electrodeprotrude outwardly from the plurality of layers on a side opposite theouter surface of the expandable member.
 17. A medical device forsympathetic nerve ablation within a body passageway, comprising: acatheter shaft; an elongate balloon coupled to the catheter shaft, theballoon being capable of shifting between an unexpanded configurationand an expanded configuration; and a plurality of elongate electrodeassemblies each constructed as a flexible circuit having a plurality oflayers, the plurality of electrode assemblies being bonded to an outersurface of the balloon; wherein each of the plurality of electrodeassemblies includes a temperature sensor comprising less than fivepercent of a maximum thickness of each of the plurality of electrodeassemblies.
 18. The medical device of claim 17, wherein the temperaturesensor is a sputtered thermocouple embedded between the plurality oflayers.
 19. The medical device of claim 17, wherein at least a region ofthe flexible circuit along the temperature sensor has a substantiallyconstant thickness.
 20. The medical device of claim 17, wherein theflexible circuit is free of a radial protrusion adjacent to thetemperature sensor.